Electromagnetic device



Jan. 13, 1959 G. REED 2,869,048

ELECTROMAGNETIC DEVICE Filed May 18, 1953 35 INVENTOR.

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United States Patent ELECTROMAGNETIC DEVICE Gabriel Reed, London,England, assignor to Ultra Electric, Inc., Wilmington, Del., acorporation of Delaware Application May 18, 1953, Serial No. 355,424

Claims priority, appiication Great Britain May 22, 1952 3 Claims. (Cl.317-165) This invention relates to an improved electromagnetic device,of the kind comprising a fixed magnetic member (stator) cooperating witha movable magnetic member (armature) and excited by a solenoid toproduce movement of the said armature against a load force, for examplea force exerted by a spring, and in which the said movement is requiredto bear a given relationship with the current fed to the device, forinstance a linear relationship.

It is known to provide in a device of the kind referred to a solenoidinto which an iron armature in the form of a plunger is attractedagainst a constraining force, the desired relationship between currentand movement being obtained by suitable shaping of the end of theplunger and/or of a fixed pole-piece in the solenoid. All such knownarrangements have the common characteristic that the working air-gapvaries in length with the movement of the plunger. In these priorarrangements the plunger is large and heavy. The consequent inertia ofthe system precludes its use when rapid response to change in current isrequired, or when the arrangement is subject to external accelerationsas, for example, when used in aircraft.

The object of the invention is to provide an electromagnetic device ofthe kind referred to, in which a small and light armature is used and inwhich the relationship between the current fed to the device and theforce exerted against the load force may be selected from between widelimits.

According to the present invention, an electromagnetic device in whichmovement of the armature against a load force, more particularly aspring, bears some desired relationship to the exciting currentcomprises fixed and movable cooperating magnetic members whose relativemovement is such that the perpendicular distance across the air-gapsbetween juxtaposed faces of the said members remains constant, and suchthat the overlapping areas of the said juxtaposed faces change with saidmovement and in which one or more of either or both said faces is or areso shaped that the said overlapping areas change in a non-linear mannerwith respect to said movement.

The invention will be better understood after reading the followingdescription of several exemplary embodiments with reference to theaccompanying drawings in which:

Figure 1 is an elevational view of an electromagnetic device of E-shapedconstruction;

Fig. 2 is an end view of the armature of Figure 1, as seen in thedirection of the arrow A;

Fig. 3 is an exploded perspective view, partly broken away, of apot-shaped electromagnetic device;

Fig. 4 is an elevational view of an electromagnetic device comprising arotary armature; and

Fig. 5 is an end view of the armature of Fig. 4, as seen in thedirection of the arrow B.

Referring to the construction shown in Figures 1 and 2, 7

a is an E-shaped stator energized by the solenoid b and cooperating witha C-shaped armature c, the two limbs c of which are tapered in thedirection of its movement relatively to the stator, as seen in Fig. 2,but its width between the inner and outer limbs of the stator isconstant.

Referring to the construction shown in Fig. 3, 2a is a pot-shaped statorenergised by the solenoid 2b and cooperating with an annular armature2c, portions of which towards the stator are tapered by two downwardlyinclined cuts being made diametrically opposite each other, as shown inthe figure.

Referring to the construction shown in Figs. 4 and 5, the stator 3a,energised by the solenoid 3b, is provided with two opposite concaveshaped pole-pieces cooperating with a rotary armature 3c of Z-shape, theends c of which are tapered in its direction of rotary movement, asshown in Fig. 5.

The details for carrying the invention into eflect, in connection with aD. C. or an A. C. electromagnet, may be modified without departing fromthe essence of the invention aforementioned. For instance, instead ofthe stator, the armature may be energised and instead of the ends of thearmature being tapered in the direction of movement, the face of thestator cooperating with the ends of the armature may be suitablytapered.

What I claim is:

1. An electromagnetic device comprising a stator member having a coreand at least one pole face of magnetic material, an armature member ofmagnetic material mounted for parallel movement in spaced relationshipwith respect to said pole face, said movement being such that theperpendicular distance across the air-gap between juxtaposed faces ofsaid pole face and said armature member remains constant throughout itsmovement while the overlapping area of said juxtaposed faces changeswith said movement, and a winding for energizing one of said membersoperatively supported thereon, characterized by one of said juxtaposedfaces having a triangular shape in the plane parallel to the other faceand disposed such that upon movement the overlapping area of saidjuxtaposed faces increases at a greater than linear rate as the armaturemoves into overlapping relation with respect to said pole face.

2. An electromagnetic device according to claim 1, in which said coreconsists of an E-shaped member with parallel legs, said armatureconsists of a C-shaped member with its arms disposed between the legs ofsaid core,

.and the arms of said armature have a triangular shape in the planeparallel to the opposing faces of the legs of the core and have aconstant width in the plane of said core.

3. An electromagnetic device according to claim 1, in which said corecomprises two concentric, opposite, and concave pole faces and saidarmature comprises a Z- shaped rotatable member having its ends taperedalong the arcs of their movement so as to have said triangular shape andhaving its faces concentric with those of the said pole faces.

References Cited in the file of this patent UNITED STATES PATENTS293,076 Piette Feb. 5, 1884 2,127,265 Martin Aug. 16, 1938 2,337,375Cramer Dec. 21, 1943 2,738,450 Matthews Mar. 13, 1956 FOREIGN PATENTS215,679 Great Britain May 15, 1924 551,790 Great Britain Mar. 10, 1943

